The Saiyan Invasion.
So on their way to earth to pick up Kakarot, Raditz, Vegeta and Nappa get lost and take a wrong turn at the multiverse. Raditz still lands a year before the other two but they now have to these strange new enemies in their quest for Kakarot. They also learn that the saibamen can't grow in these universes.
Round 1: Raditz lands in Amity Park, the home of Danny Phantom. Somehow his ghost sense and his parents technology were able to pick up on Raditz's pod. Dani and Vlad agreed to help Danny take the saiyan down. They have one fixed up Ecto-suit they can use between them. If they beat him, They have a year to prepare for the others anyway they can.
Round 1b: Somehow the saiyans land in the ghost zone and the "real world stuff just phases through things" rule is not in effect.
Round 2: They land on mount Rushmore and the plumbers inform Ben 10 and his friends. Alien X is still off the table.
Round 3: The multiverse got a little beat up on their way through, and now The world of the Avatar is having time issues. Both Aang, Korra and there friends are alive and there is a permanent sozin's comet.
Round 4: Tremorton. The Xj series and other robotic heroes stand up against theses warriors.
Can the Western Cartoons take One of the most over the top anime villians, or will they be exploded like yamcha?